Structural Materials Commons^™

Large-Scale Graphene Film Deposition For Monolithic Device Fabrication, Khaled Al-Shurman

Graduate Theses and Dissertations

Since 1958, the concept of integrated circuit (IC) has achieved great technological developments and helped in shrinking electronic devices. Nowadays, an IC consists of more than a million of compacted transistors.

The majority of current ICs use silicon as a semiconductor material. According to Moore's law, the number of transistors built-in on a microchip can be double every two years. However, silicon device manufacturing reaches its physical limits. To explain, there is a new trend to shrinking circuitry to seven nanometers where a lot of unknown quantum effects such as tunneling effect can not be controlled. Hence, there is an …

Prediction Of Shear Strength And Ductility Of Cyclically Loaded Reinforced Concrete Columns Using Artificial Intelligence, Nicholas Gordon

UNLV Theses, Dissertations, Professional Papers, and Capstones

The shear strength and deformation capacities of reinforced concrete (RC) columns are governed by a multitude of variables related to material properties of the steel and concrete used in the design and construction of the columns. Predicting performance of RC columns using design variables is a complex, non-linear problem. The prediction of shear strength and ductility for these types of structural members has historically been performed using empirically or semi-empirically derived formulae based on experimental results. The introduction of cyclical lateral loading, such as the forces imposed on a structure during an earthquake, can result in severe degradation of shear …

A Multi-Scale Based Model For Composite Materials With Embedded Pzt Filaments For Energy Harvesting, A.E. El-Etriby, M.E. Abdel-Meguid, K.M. Shalan, Tarek Hatem, Yehia Bahei-El-Din

Centre for Advanced Materials

Ambient vibrations are major source of wasted energy, exploiting properly such vibration can be converted to valuable energy and harvested to power up devices, i.e. electronic devices. Accordingly, energy harvesting using smart structures with active piezoelectric ceramics has gained wide interest over the past few years as a method for converting such wasted energy. This paper provides numerical and experimental analysis of piezoelectric fiber based composites for energy harvesting applications proposing a multi-scale modeling approach coupled with experimental verification. The multi-scale approach suggested predicting the behavior of piezoelectric fiber-based composites use micromechanical model based on Transformation Field Analysis (TFA) to …

Seeing Red: Characterizing Historic Bricks At Sylvester Manor, Long Island, Ny 1652-1735, Martin John Schmidheiny

Graduate Masters Theses

The goal of this project is to develop a basic material characterization of the bricks excavated at the site of Sylvester Manor on Shelter Island, New York. In the early Manor period of 1650-1690, this early Northern provisioning plantation supplied Barbadian sugar operations and pursued mercantile interests independent of state control. Accounting for the range of production defects and material characteristics of the bricks suggests on-site or local manufacture as a regional ceramic industry developed. Qualitative visual analysis and petrographic thin-sections were used to characterize the internal composition, variation and production evidence in the bricks. Interpreting the results of this …

Development Of Micro-Hall Devices For Current Sensing, Thomas White

Graduate Theses and Dissertations

In this work, micro-Hall devices were developed for the purpose of sensing current within a high temperature and high power environment. GaAs HEMT, InGaAs pHEMT, and GaN HEMT structures were studied. These structures were grown by molecular beam epitaxy. Processing techniques including photolithography, metallization, Si deposition, wet etching, and dry etching were studied. Electrical characterization measurements including low frequency noise, Hall effect, sensitivity, capacitance-voltage, and current-voltage were performed.

Electron mobility and sheet carrier density studies were performed for both the InGaAs pHEMT and GaAs HEMT structures. Results indicated the InGaAs pHEMT was superior and thus fabricated as the micro-Hall device. …

Atom-Based Geometrical Fingerprinting Of Conformal Two-Dimensional Materials, Mehrshad Mehboudi

Graduate Theses and Dissertations

The shape of two-dimensional materials plays a significant role on their chemical and physical properties. Two-dimensional materials are basic meshes that are formed by mesh points (vertices) given by atomic positions, and connecting lines (edges) between points given by chemical bonds. Therefore the study of local shape and geometry of two-dimensional materials is a fundamental prerequisite to investigate physical and chemical properties. Hereby the use of discrete geometry to discuss the shape of two-dimensional materials is initiated.

The local geometry of a surface embodied in 3D space is determined using four invariant numbers from the metric and curvature tensors which …

The Development Of A Laminated Copolyester Electric Guitar, Addison S. Karnes

Electronic Theses and Dissertations

This thesis is an investigation of the fabrication and assembly methodologies employed in the development of a proof-of-principle prototype electric guitar composed of laminated copolyester. The objective of the project was to develop the processes and procedures to create an optimized physical and visual bond between layers to minimize vibratory dissipation, thus maximizing sustain. A high speed CNC router, abrasive waterjet, laser engraver-cutter, as well as various manual fabrication and assembly methods were investigated in the construction of the guitar prototypes. The lamination processes explored include low-temperature, heat-assisted pressure bonding, solvent and chemical welding, and contact adhesives. The project concluded …

Early-Age Hydration Studies Of Portland Cement, Fengjuan Liu

Electronic Theses and Dissertations

Our current knowledge on cement hydration during setting is based on the discrete observation of hydrated paste. An advanced micro/nano-level technique which can perform the in-situ observation on the continuous hydration of cement paste is demanded. In this study, Raman spectroscopy (RS) was chosen as such a method to continuously investigate wet pastes. The objective of this research is to explore the hydration process and microstructural development of fresh pastes with this technique. This research was conducted in three phases. First, the RS analysis was used to continuously observe the cement hydration from 20 minutes after mixing to 9 hours. …

High Strength Steel Fiber Reinforced Flow-Able Or Scc Concrete With Variable Fiber By Volume Fractions For Thin Plate And Shell Structures, Abebe Berhe

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this study is to incorporate discrete, short, mechanically deformed, small diameter steel fibers into high strength concrete with f'c > 70 MPa (10 ksi) in an attempt to reduce and partially eliminate the need for steel rebar in concrete construction. By introducing steel fibers to high strength concrete mixture, the overall tensile, compressive and shear strength of the mixture can be improved immensely thus, replacing portions or major parts of the longitudinal, temperature and shrinkage reinforcements. The reduction or elimination of longitudinal and transverse reinforcements in the construction of structural or non-structural members can result in savings in …

Fiber Length And Orientation In Long Carbon Fiber Thermoplastic Composites, Imad Hanhan, Connor Sullivan, Bhisham Sharma, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Carbon fiber composites have become popular in aerospace applications because of their lightweight yet strong material properties. The injection molding process can be used to produce discontinuous fiber composites using less time and resources than traditional methods, thereby broadening carbon fiber composites’ applications in different industries. Utilization of longer fibers offers more load carrying capability and superior strength properties for injected molded composites. Since the fiber length and the orientation distribution in Long Fiber Thermoplastics (LFTs) directly affects LFT composites’ material properties, there is a need to study the microstructure of LFTs and characterize fiber length and orientation distributions. Therefore, …

Finite Element Analysis Of Bolted Connections Under Fire, Ke Liu, Qiaqia Zhu, Amit H. Varma

The Summer Undergraduate Research Fellowship (SURF) Symposium

Over the course of human history, fire disasters are one of the major catastrophes that causes loss of lives and properties. In order to ensure building safety against fire, civil engineers seek to understand the behavior of structures at high temperatures. Moreover, they need to study the behavior of bolted connections, given the important role it plays in steel structures. Sarraj (2007) proposed a plate-bearing computational model used to describe this behavior; however, it has never been experimentally verified. Prior to this specific project, a series of single-bolted connection tests at 400°C and 600°C were conducted in the Bowen Laboratory …

Molecular Exploration Tool, Weiyi Cao, Nicolas Onofrio, Alejandro Strachan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Density Functional Theory (DFT) which is based on quantum mechanics theory has been broadly used to compute the energy and the structure of molecules and solids. However, the DFT method is limited when running calculations for a large system and only thousands of atoms can be solved. Alternatively, Molecular Dynamics (MD) simulation can be used to investigate the properties of the atomic system for large systems in the classical mechanics approximation. When running the MD simulation, the electronic structure is approximated by Force Fields (FF) which can be parametrized against DFT calculations. Nevertheless, the accuracy of the MD results and …

Bio-Inspired Helicoidal Composites: 3d Printing And Experiments, Michael E. Jones, Pablo Zavattieri, Nobphadon Suksangpanya

The Summer Undergraduate Research Fellowship (SURF) Symposium

Materials that are impact resistant enough for personal protection in sports, transport, and combat are not also lightweight, strong, tough, and impact tolerant. Nature can provide inspiration for novel materials that can meet these needs. The hierarchical composite of the stomatopod’s, or mantis shrimp’s, dactyl club has been shown to have high impact resistance and damage tolerance due to its helicoidal fiber reinforcement(1,2). Analyzing helicoidal composites of different pitch angles (angles between adjacent rows of fibers) under quasi-static, displacement-controlled loading has provided insights into the fracture mechanisms of the composite structure and how they affect the macroscopic properties of the …

He+ Ion Irradiation On Tungsten Surface In Extreme Conditions, George I. Joseph, Jitendra Tripathi, Sivanandan S. Harilal, Ahmed Hassanein

The Summer Undergraduate Research Fellowship (SURF) Symposium

Higher melting point (3695K), lower sputtering yield and most importantly, lower in-bulk, and co-deposit retention at elevated temperature makes tungsten (W) as a potential candidate for plasma-facing component (PFC) in the international thermonuclear experimental reactor (ITER)-divertor. Helium ion (He⁺) bombardment on W can cause wide variety of microstructural evolution, such as dislocation loops, helium holes/bubbles and fibre-form nanostructures (Fuzz) etc. In this work, 100 eV He⁺ ion irradiation, at temperature ranges from 500°C to 1000°C, will be performed on mechanically polished mirror like W surfaces. The surface modification and compositional analysis, due to ion irradiation, will be …

Microstructure Development Of Granular System During Compaction, Chen Shang, Marcial Gonzalez

The Summer Undergraduate Research Fellowship (SURF) Symposium

Granular materials is the second most manipulated material in the industry today. They are easy to transport and more and more newly developed materials cannot stand the process of traditional casting, like energetic materials and bio-materials, but will survive the powder compaction process. Having a better understanding of the microstructure development of granular systems during compaction process, especially for particles that will heavily deform under loading, will give an insight of how to better process the powders to produce materials with overall better performance comparing to bulk materials. The main theory and mechanism applied are Hertz law and nonlocal contact …

Crack Propagation Simulation Tool, Nilofer Rajpurkar, Hojin Kim, Alejandro Strachan

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the massively engineered world that exists today, understanding material behavior is of paramount importance in caring for human safety in design. Molecular dynamic simulations on crack propagation through materials allow visualization of material behavior under stress. The tool, developed by the nanoHUB group as a part of the Network for Computational Nanotechnology at Purdue University, makes performing such simulations accessible to undergraduate students, highly qualified researchers, and all those in between. First, the input deck for the simulation parameters was simplified from the complex, language-specific code into a simple, user-friendly Graphic User Interface (GUI). Several interesting example cases were …

Dynamic Response Of Textile Material Under Transverse Impact, Yuchen Zheng, Matthew C. Hudspeth, Weinong W. Chen

The Summer Undergraduate Research Fellowship (SURF) Symposium

Textile materials, such as Dyneema and Kevlar, are the major raw materials for state of the art military or personal security armor vests. However, in impact experiments, actual observed penetration speed is much lower than theoretically predicted penetration speed. Each armor vest is composed of high performance yarns which are woven together to form fabrics, which when stacked together form a vest. Understanding penetration behavior of yarns is essential to evaluate the performance of fabric, which will be useful for the design of better vests. The project is composed of three parts: static experiments, dynamic yarn experiments and dynamic fabric …

Synthesis And Thermoelectric Properties Of Cusbs2, Tianyue Gao, Haiyu Fang, Yue Wu

The Summer Undergraduate Research Fellowship (SURF) Symposium

Copper antimony sulfide, CuSbS2 nanoparticles have a large potential of being a good thermoelectric material because they are made up of earth abundant elements. Thermoelectric materials can convert thermal energy into electricity, so that the wasted energy can be saved. Also, by using this earth abundant material, we can make thermoelectric materials much cheaper. The hypothesis of this study is that CuSbS2 could have a large Seebeck coefficient, one of the most important factors of thermoelectric materials, because of the complexity of its band structure. The other hypothesis is that thermal transport could be significantly suppressed through nanostructuring. There are …

Durability Of Silane Sealer In A Highly Alkaline Environment, Cameron David Murray

Graduate Theses and Dissertations

Alkali-silica reaction (ASR) is a chemical reaction between siliceous minerals present in certain aggregates and alkalis in the concrete pore solution. The reaction can lead to expansion and severe damage in concrete members. One method to mitigate ASR expansion is to use a penetrating sealer such as silane. A set of columns located in a food preparation facility was treated with silane and a complimentary laboratory study was performed. A cleaning regimen involving application of an alkaline cleaner is employed at the facility, followed by rinsing with hot, pressurized water. The purpose of this research is to evaluate the effectiveness …

Finite Volume Numerical Analysis Of The Thermal Property Of Cellular Concrete Based On Two And Three Dimensional X-Ray Computerized Tomography Images, She Wei, Yang Yonggan, Xie Deqing, Zhang Yunsheng

International Conference on Durability of Concrete Structures

Cellular concrete is one kind of lightweight concrete, which are widely used in thermal insulation engineering project. In this study, a three dimensional (2D and 3D) finite-volume-based models was developed for analyzing the heat transfer mechanisms through the porous structures of cellular concretes under steady-state heat transfer condition and also for investigating the differences between 2D and 3D modeling results. 2D and 3D reconstructed pore networks were generated from the microstructural information measured by a 3D image captured by X-ray computerized tomography (X-CT). In addition, the 3D-computed value of the effective thermal conductivity was found to be in better agreement …